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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3eff0511ba92e1df81533304417aa84794d038e45b6878d527ce3777b50c5396' 
  AND token = 'wsxy9rtdB0Ki/jTDNSy+vitTdGTExC2ESpM8M6eovrg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}